The present invention relates to a method and apparatus for freezing the content of a pipe in a non-invasive manner.
There are various situations where it is desirable to terminate the flow of fluids through a pipe. One example involves defective valve replacement. When a valve leaks, routine maintenance of equipment, or replacement of the valve generally is not practical without shutting down the entire system and draining the pipe. Shutting down of the entire system, however, is not practical when critical operations must be maintained using the system.
A second example is where a valve was not installed in a branch line during original construction, but must be installed now in the pipe without shutting down the entire system. In either case, a freeze of the pipe contents would be desirable upstream and downstream of the desired valve site in order to prevent loss of fluid, chemical treatment, or both. In addition to advantageously avoiding drainage of the system, freezing would eliminate the need for refilling and venting of air from elements of the fluid network (e.g., heat transfer equipment and coils).
With the foregoing difficulties as a background, several devices and methods have been developed for plugging an existing pipe to stop the flow of fluid through the pipe. Some of those devices and techniques involve insertion of a plug through a hole in the pipe or otherwise, and in some cases, inflation of the plug after insertion. At least one device and technique involves freezing of the material which is used to inflate the plug and/or external application of a cooling device to the pipe which assists in freezing of the material in the plug.
With regard to the devices and techniques that insert a plug into the contents of the pipe, the use of such devices and techniques is limited to those pipes which are compatible with the size and shape of the plug. If a wide range of pipe sizes and shapes are to be plugged, multiple plugs must be provided, each having a different size and/or shape. If the material which makes up the plug is flexible and/or the plug is inflatable, then care must be taken to ensure that such material is compatible with the contents of the various pipes into which the plugs will be inserted. The process of inserting and/or inflating the plug also can be rather complicated.
Still other devices and techniques provide a cooling device only to an outside surface of the pipe. Such devices draw heat from the contents of the pipe, through the pipe itself, and eventually freeze the contents of the pipe to form a plug. Many of those devices and techniques, however, are designed for a particular pipe diameter. It is difficult to apply such devices to pipes having different diameters without providing multiple devices, each of which is designed for a particular pipe diameter. The use of multiple devices, however, is seldom practical. Those devices must be carried by the user and/or stored. As a result, such devices and techniques tend to be cumbersome and wasteful of space.
Some of the devices that are applied externally also fail to adequately contain the cryogenic fluids that are used to draw the heat through the wall of the pipe. Some are permeable to the cryogenic fluid, have no seals, or have inadequate seals. As a result, a substantial amount of the cryogenic fluid is allowed to escape. When used with Freon, for example, all or most of the Freon escapes into the atmosphere. This, however, is not consistent with recent environmental efforts and regulations directed to the reduction of Freon emissions.
In addition, many of the existing devices that are applied externally have structures that completely surround the pipe to be frozen. This makes it difficult, if not impossible, to freeze the contents of a pipe locally where the pipe has external obstacles, such as a branch pipe extending out from the pipe to be frozen.
There is consequently a need in the art for a non-invasive device and/or method capable of locally preventing flow through a pipe, by freezing the content of a pipe, without the need for insertion and inflation of a plug. There is also a need for a device and/or method capable of freezing the content of a pipe, without having to introduce any structure through the wall of the pipe, without having to provide multiple devices to accommodated different diameters of pipe, without being limited to use at locations along the pipe where there are no external obstructions, and/or while minimizing the escape of cryogenic fluids into the atmosphere.
Hereinafter, the term "cryogenic" is used in its broadest sense. It encompasses not only subject matter involving super-cooled fluids, but also subject matter involving refrigerants instead of super-cooled fluids, regardless of whether applied using an open flow arrangement or a closed refrigeration loop.